Oil Quench Hardening

Oil quench hardening is the preferred method for hardening for most steel grades of investment castings. It’s preferred because it enables the casting to achieve its required strength and hardness properties while posing less risk of distortion than water or polymer quench processes.

Capability

Oil hardening for investment castings is performed in our numerous batch-type internal quench atmosphere furnaces, which are exceptional for their process and lot control capabilities. All of these furnaces are certified to the temperature uniformity requirements of AMS 2750 , and our largest furnace capable of performing oil quench hardening has internal working dimensions of 36”W x 72”L x 42”H and can handle weights of up to 7000 pounds.

Process

The process of oil quench hardening for investment castings is performed by first fully austenitizing the steel in the temperature range of 1500°F – 1650°F depending on the steel grade. It is held at this temperature for a time proportionate with the part cross-section.The entire austenitizing process is carried out under a protective carbon-controlled atmosphere that protects the surface quality of the parts under high temperature. Once soaked at the austenitizing temperature for the appropriate amount of time, the load is quenched in agitated oil to produce a fully hardened martensitic microstructure. From this point, the parts are tempered down to the specified hardness range to improve toughness while reducing overall strength.In cases where parts are especially distortion sensitive, ThermTech will modify the oil quench process to minimize or eliminate these problems completely while still achieving the required material properties. For extreme distortion tolerances, take a look at our marquench hardening or austempering services.

Recommendations

Please be aware that lower final hardness ranges that require tempering above 900°F will result in temper oxide formation on most steel grades. Because of this, ThermTech offers blasting services to remove that oxide formation and improve the surface finish. Alternatively, we also offer vacuum oil hardening, which can result in a bright surface finish after hardening (depending on the tempering temperature employed)

ThermTech offers oil hardening processes of investment castings for many low-alloy steel grades. Some of the most common materials we offer this process for include:

Normalizing is one of the simplest heat-treatments that can address refining (or normalizing) the microstructure and equalizing the effects of the range of temperatures the material has been subjected to during the forging operations.

ThermTech is a pioneer in the abilities to polymer quench large section sizes of forgings that require superior mid-radius hardness and mechanical properties for forgings needed by the fracking companies components.

We have come across several customers who perfer their forgings be marquenched in molten salt to minimize the risk of cracking during the quench operations and to minimize distortion on long, thin products.

The full annealing process involves taking a casting to a temperature above the critical eutectoid temperature in the 1475F-1650F range for a length of time commiserate with the cross section size and then slow cooled to promote a ferritic microstructure.

To insure that the steel castings are capable of achieving full surface hardness during subsequent hardening processing the castings may require a carbon restoration of their surfaces and we have several furnaces capable of doing this.

This process involves heating the parts above the critical temperature and slow cooling them in order to create a microstructure both more refined due to recrystallization and softer and more ductile regarding hardness and mechanical properties.

Many machined components have intricate details or section size changes that lend themselves to being crack-prone.We watch for problem jobs like this and we can run them through our neutral hardening salt furnace with molten salt quench to avoid cracking.

Carbonitriding can be performed on both heavy gage stampings and low alloy machined components. Typically the case depths needed are in the 0.003" to 0.020" range due to the low hardenability of the steels involved.

Several people in our Quality Department maintain the specification library, write part number specific processes and manage the sub-contracted mechanical testing to insure your parts are exceeding the mechanical requirements for your application.

A vacuum stress relief of molds allows a more uniform looking textured surface during subsequent usage. We can handle a die or mold up to 36" wide x 32" high x 72" long with a total piece weight of 10,000 pounds.

Some Tool and Die materials like S-5, 52100, O-1, & O-6 require oil quench hardening. ThermTech has several furnaces capable of hardening these materials with the largest being 36" wide x 42" high x 72" long.

Often several tool steels supplied in the as-cast conditions definitely need a carbon restoration due to the high carbon content of those materials and the natural de-carburization environments of the casting processes.

To straighten out a material post-hardening when they are at their most brittle we employ a process involved fixturing the part during the tempering operation where the material has more ductility and takes a set to a straighter/flatter configuration.

Tool & Die products shaped in cylindrical form require straightening by mechanically pressing the parts with some localized heat put on an area to prevent gross cracking due to the brittleness of the material involved.

Gears made from plain carbon steels like 1017, 1018, and 1020 materials and low alloys such as 1117 & 12L14 require ammonia additions at the end of the carburizing process to increase the surface hardness of splines and teeth.

ThermTech has the unique capability of Carburizing gears and quenching them into molten salt to help minimize distortion. We have two furnaces capable of marquenching gears in furnaces with load sizes of 36" wide x 48" high x 72" long.

ThermTech can age harden several varieties of Aluminum to the T-6 or T6 condition. We've aged smaller diameter tubes up to 12' lengths and can handle many varieties of parts up to 60" in diameter to 80" tall.

Stress Relieving can help minimize the distortion seen by the part due to the machining stresses that can be built up by the manufacturing of the part. Contact us for a quote. We can handle a wide variety of sizes for this process.

Many times the end usage of Investment Castings don't require any hardening of the material for the parts to work, however, the parts may require a stress relieve to remove any stress caused by the casting process so the parts maintain their tolerances.

Due to partial or total surface decarburization that stems from the investment casting process a procedure known as carbon restoration is used to restore the proper carbon content at the surface of the parts in question.

Several types of low alloy investment castings require water quench hardening in order to achieve the proper hardness or mechanical properties. These alloys usually are plain carbon steels such as 1018, 1020, 1030, 1035, 1040, & 1045 materials.

Due to most of the investment castings we process being on the small size (less than 5 lbs each) we offer both hand-blast and a rubber belt tumble-blast options to properly and quickly turn around any cleaning requirements.